For me, anything more than 2.25" wide needs more than a 1/4" seam or it won't be full. If I'm not sure what I need, I sew several inches than pull it over and see if the seam is correct for the binding width. If not, I adjust.
I never use a seam guide, I just go by what I've got sticking out from the edge of the narrow straight stitch foot. I know if I can see 2-3 threads, that is right about a scant 1/4". If what I'm sewing is coming out a bit short, I sew so less is sticking out, and if it seems wide, then I sew with more sticking out.